Split bearing, cage for split or non-split bearing and method of cutting a member of a split bearing

ABSTRACT

A split bearing, a cage for a split or non-split bearing and a method of cutting a member of a split bearing is related in this disclosure. The split bearing has at least one component, such as the outer race, split, i.e., formed into at least two parts, each part defining two longitudinally extending surfaces which mate with a corresponding longitudinal surface of the adjacent part such that the mating surfaces define a helix in their longitudinal extent. The cage of the split or non-split bearing includes two annular parts that in assembly define a plurality of cavities each one adapted to receive a roller member of the bearing. Each of the two annular parts including at least two pieces joined together by a tongue and groove connection. The method of cutting a member of a split bearing involves cutting the member longitudinally such that the cut mating surfaces, define a helix in the longitudinal direction.

BACKGROUND OF THE INVENTION

1. Field of The Invention

The present invention relates to the field of bearings, and inparticular to split bearings.

2. Background Discussion

Split bearings, i.e., a bearing with both the inner and outer raceformed in two parts have been used in industry for various applicationsfor a number of years. U.S. Pat. No. 3,304,140 is an example of such abearing.

One of the important advantages of a split bearing is its ease ofassembly and disassembly. During periodic maintenance or overalloperations, the disassembly feature is quite helpful in avoidingunnecessary or excessive dismantling of associated equipment.

A disadvantage of split bearings is that they are more expensive tofabricate, and also they are more prone to failure due to the fact thatthey comprise sections (parts such as noted above) which are necessarilyload bearing. Whenever a structural part is subject to load, forming thestructural part in sections inherently tends to weaken the part. The cutsurface, in particular, can experience fretting. Fretting can lead tobearing failure. One reason fretting is a problem is because the matingcut surfaces move relative to each other.

Accordingly, bearing designers have focused their attention on reducingthe relative motion of the cut surfaces.

SUMMARY OF THE INVENTION

The present invention also focuses on the cut surfaces. In particular,on how they can be better mated to avoid relative motion.

The structural parts of most bearings are generally cylindrical inshape. Certainly, the inner and outer race and the ball or roller cageare cylindrical. It is noted that for a rotating cylinder a compatibleform is a helix (for example, a gear and gear teeth or a screw and screwthreads). It was believed that a helical cut surface, i.e., a surfacewhich extends along a helical path about a cylinder when viewed in thelongitudinal direction of the cylinder, would provide the optimum matingsurfaces which would reduce, if not eliminate, relative motion.

A helix is a curve wound around the outside of a cylinder or coneadvancing uniformly along the axis as it winds around the outer surfaceof the cylinder. (Elements of Mechanisms, Doughtie and James, John Wiley& Sons, Inc., 1954, pages 303-305).

FIG. 1 illustrates a line (H) wound about a cylinder (C) helically, Thehelix angle (∝), is the angle that a straight line tangent to the helixat any point makes with an element of the cylinder. The lead (L) is thedistance by which the helix advances along the longitudinal axis A--A ofthe cylinder for one turn around the cylinder, while the pitch (P) isthe distance between a point on the helix and the corresponding point onthe next turn of a single helix.

With the present invention, the pitch (P) and helix angle (∝) are high.

Until the advent of the wire electric discharge machine, cutting acylinder wall such that the cut surface extends along a helix whenviewed in its longitudinal extent was virtually impossible. Anotherdirection to accomplish this helix would be through the development ofthe water jet cutting machine.

A split bearing, i.e., a bearing with at least its outer race formed inat least two parts, is proposed, and in particular a split bearing withboth its inner and outer race formed in at least two parts, such thatthe cut and mating surface(s) are developed helically along thelongitudinal axis of the bearing.

The helical cut surface(s) would each be substantially perpendicular tothe longitudinal axis and would develop as a helical line that could beat any helix angle to the longitudinal axis.

The split bearing proposed would have all its split surfaces formed by awire electric discharge machine. Accordingly, the present invention alsocontemplates a method of producing a cut surface to form a split bearingwhere at least the outer race of the bearing is cut into at least twopieces.

The present invention also contemplates forming edge grooves adjacentthe race flanges for improved lubrication. These grooves are provided inaddition to the annular grooves in a bearing housing which serve as thetypical oil or grease carriers in anti-friction bearings. These groovesincrease the lubrication of the rolling components, and retain greaseand oil at the point needed for good lubrication. There is also amanufacturing benefit because the grinding wheels needed to surfacefinish the race have less material to remove and would not need to beformed to produce the corner shape that is typical in bearing races.These corners also would minimize stress concentration in the heattreating process of the races.

The present invention also contemplates a cage design used with a splitor a non-split bearing, the cage is split horizontally as well asaxially to form a four piece assembly. The four piece assembly isdie-cast more efficiently and is riveted together in halves at the timeof roller installation and these halves are then held together with aspring locking clip that will have shear capability if the halves wouldever bend in a centrifugal load situation. The locking spring clip wouldhave to be sheared to separate the halves. Also, the ease of assembly isimproved and its position is more precise because of a tongue and grooveassembly of the halves. This tongue and groove may also be provided witha cylindrical fit or notched to further limit movement (See FIG. 14).

Because of the need for draft angles in the die-casting process, thecavities that retain the rollers will have smaller angular fits with therollers and the small draft angles will retain lubrication that servesto improve the life of the roller cage and the rollers.

Ease of cage assembly is also a benefit. Semi-tubular rivets will holdtwo of the four die-cast parts as the rollers are installed. This cagedesign also will control the movement and clearance of the rollers inthe cage more precisely and allow better concentricity and balance forthe assembled bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

Fourteen figures have been selected to illustrate a preferred embodimentof the various aspects of the present invention. The figures areschematic but nonetheless sufficiently detailed to enable those skilledin the art to practice the present invention in all its aspects.Included are:

FIG. 1, which is an explanatory view illustrating the general form of ahelix on a cylinder;

FIG. 2, which is a further explanatory view illustrating a typical helixcut on a split bearing;

FIG. 3, which is exploded perspective view of a split bearing whichembodies all the various aspects of the present invention;

FIG. 4, which is a side view, partly in cross section of an outer raceof a split bearing according to the present invention;

FIG. 5, which is a side view, partly in cross section of an inner raceof a split bearing according to the present invention;

FIG. 6, which is an enlarged view of detail A of FIG. 4;

FIG. 7, which is a plane view of an assembled bearing cage and rollerbearings according to the present invention;

FIG. 8, which is exploded view showing the two pieces of the bearingcage of FIG. 6;

FIG. 9, which is a partial inside side view of the bearing cage of FIG.6;

FIG. 10, which is a partial top view of the bearing cage of FIG. 6showing a tongue and groove attachment;

FIG. 11, which is a partial and perspective view of the bearing cage ofFIG. 6 showing the tongue and groove attachment;

FIG. 12, which is a front view of the bearing cage clip;

FIG. 13, which is a front view of an inner race clamp; and

FIG. 14, which shows the cylindrical tongue and groove.

DETAILED DESCRIPTION OF THE FIGURES

The helix H as shown in FIG. 1 when generated on a bearing part inaccordance with the present invention, is shown in FIG. 2.

In FIG. 2, the cylinder C becomes a cylindrical part of a bearing andthe line H becomes the helical cut surface. The helix angle illustratedis much larger than that shown in FIG. 1 because in practice the bearingpart is cut into at least two parts.

A machine and procedure for making such a helical cut are disclosed, forexample, in U.S. Pat. No. 5,290,987. The disclose of this patent ishereby incorporated by reference.

Any cylindrically shaped part of the bearing may be fabricated toinclude at least two parts formed as such by being cut to define twopairs of mating longitudinally extending surfaces. For example, the lineH of FIG. 2 represents one pair of mated longitudinally extendingsurfaces formed on a helix of the cylindrical part C. It is necessary togenerate this helical cut by passing a line through the cylinder axis asthe part is rotated through the desired helical angle.

Turning to FIG. 3, a split bearing 10 is shown embodying the variousfeatures of the present invention. The bearing 10 includes an uppercartridge 12 and a lower cartridge 14. These cartridges form an outerhousing of the bearing and are connected to each other by bolts 16. Thecartridges 12 and 14 are shown to include mating surfaces 12a, 12b whenconnected. These surfaces are shown as straight surfaces and not ashelical. However, these surfaces may be formed as helical surfaces.

Mounted within the cartridges 12 and 14 are an outer race 18, an innerrace 20, a cage 22 with roller elements 24, two clamping rings 26 and 28and two seals 30 and 32. As shown, the inner race 20 is formed in twoparts with helically cut mating surfaces 20a, 20b. The outer race 18 isalso formed in two parts with helically cut mating surfaces 18a, 18b(shown in FIG. 4). The surfaces 18a, 18b and 20a, 20b are formed bycutting the respective races 18 and 20 with a machine similar to thatnoted above.

The races 12 and 14 are shown in more detail in FIGS. 4 and 5, with FIG.6 showing an enlarged view A of a portion of both races, but with theillustration reproduced from that of FIG. 5 only.

The outer race 18 has parallel flanges 34 separated by a roller memberengaging surface or land 36. At the two edges defined by the flanges 34and the surface 36, there is defined a lubricating groove 38. Spacedabout the outer race 18 are several lubricating bores 40.

The inner race 20 includes a roller member engaging surface or land 42which coincides in width to the width of surface 36. On either side ofthe surface 42 there is included a recess 44 in which a clamp 46 (FIGS.13-14) is received. At each longitudinal end of the inner race 20 thereis situated a flange 48. At the two edges defined by the flanges 48 andthe surface of its corresponding recess 44 there is defined alubricating groove 50 similar in shape and purpose to lubricating groove38 (FIG. 6). A similar groove 50 is defined by each edge of the surface42 and the surface of the adjacent recess.

The cage 22 includes a plurality of roller members 24. The rollermembers 24 are supported by two support brackets 52 and 54 which arepreferably die cast. Each bracket 52 and 54 is further made into pieces52a, 52b and 54a, 54b. These pieces are joined together by rivets 56,while the joined pieces or brackets 52 and 54 are themselves joined bythe tongue and groove arrangement 58 (FIGS. 10 and 11) at two places. Atthe tongue and groove arrangement 58, the brackets 52 and 54 and thetongue and groove arrangement 58 define a recess 60 which receives aspring locking clip 62 (FIG. 12). The clip 62 serves to assist inholding the tongue and groove arrangement in place.

As assembled, the brackets 52 and 54 form a plurality of cavities 64each of which receives a roller element 24. Because the pieces 52a, 52band 54a and 54b are die cast, the sides 66 define a draft angle whichserves to retain lubrication (FIG. 9).

The clamp rings are assembled about the inner race which holds the raceto the shaft, then the roller cage is mounted.

When the assembled bearing cage is mounted on the inner race and theouter race is placed in assembly, two inner race clamp rings 26 and 26are mounted, one in each of the recesses 44. FIG. 13, shows that eachring comprises two pieces 26a, 28a and 28a, 28b. The two pieces areclamped together by bolts received in openings 68, which may bethreaded, if desired.

The bearing 10 is assembled easily and efficiently by first placing theinner race about the shaft on which it is mounted. This is followed bythe clamp rings which are tightened down on the inner race and positionthe bearing cage assembly. The bearing cage is then mounted into it'sassembled form. Next, the seals are positioned and then the outer raceis put in place, and finally, the cartridges are inserted and tighteneddown. This final step insures that all cut helix surfaces are broughtinto tight engagement.

The bearing 10 is, as noted, easy to assemble and disassemble. As aresult, routine maintenance will not require dismantling the entiremachine when all that is necessary is a bearing replacement.

What is claimed is:
 1. A split bearing, comprising:an inner annular racehaving a longitudinal extent; an outer annular race having alongitudinal extent; a plurality of roller members; and means forretaining the plurality of roller members between the inner race and theouter race, wherein at least said outer race includes at least twoparts, each part defining two longitudinally extending surfaces whichmate with a corresponding longitudinal surface of the adjacent part,said surfaces defining a helix in their longitudinal extent.
 2. Thesplit bearing as defined in claim 1, wherein at least said outer raceincludes spaced apart annular flanges and an annular lubricating grooveadjacent each flange.
 3. A split bearing, comprising:an inner annularrace having a longitudinal extent; an outer annular race having alongitudinal extent; a plurality of roller members; and means forretaining the plurality of roller members between the inner race and theouter race, wherein at least said outer race includes at least twoparts, each part defining two longitudinally extending surfaces whichmate with a corresponding longitudinal surface of the adjacent part,said surfaces defining a helix in their longitudinal extent, and saidinner race includes at least two parts, each part defining twolongitudinally extending surfaces which mate with a correspondinglongitudinal surface of the adjacent part, said surfaces defining ahelix in their longitudinal extent.
 4. The split bearing as defined inclaim 3, further comprising a pair of annular clamps, wherein said innerrace includes a land on which said plurality of roller members areengaged and a clamp recess on each side of said land for receiving arespective one of said annular clamps, each clamp recess defininglongitudinally spaced apart edges, and wherein each clamp recess definesspaced apart annular lubricating grooves adjacent the longitudinal edgesof each clamp recess.
 5. A split bearing, comprising:an inner annularrace having a longitudinal extent; an outer annular race having alongitudinal extent; a plurality of roller members; and means forretaining the plurality of roller members between the inner race and theouter race, wherein at least said outer race includes at least twoparts, each part defining two longitudinally extending surfaces whichmate with a corresponding longitudinal surface of the adjacent part,said surfaces defining a helix in their longitudinal extent, and saidmeans for retaining includes an annular cage having two annular partsand at least one clip for securing said two annular parts together, saidtwo annular parts define, in assembly, a plurality of cavities each onereceiving one of said plurality of roller members, each of said twoannular parts including at least two pieces joined together by a tongueand groove connection.
 6. The split bearing as defined in claim 5,wherein each cavity is defined by said two annular parts with thelongitudinally spaced edge surfaces of each cavity being defined by adifferent one of said two annular parts, and wherein said longitudinallyspaced edges surfaces are tapered radially outwardly toward the centerof the bearing.
 7. A split bearing, comprising:an inner annular racehaving a longitudinal extent; an outer annular race having alongitudinal extent; a plurality of roller members; and means forretaining the plurality of roller members between the inner race and theouter race, wherein at least said outer race includes at least twoparts, each part defining two longitudinally extending surfaces whichmate with a corresponding longitudinal surface of the adjacent part,said surfaces defining a helix in their longitudinal extent, and saidmeans for retaining includes an annular cage having a longitudinalextent, said cage including at least two parts, each part defining twolongitudinally extending surfaces which mate with a correspondinglongitudinal surface of the adjacent part, said surfaces defining ahelix in their longitudinal extent.
 8. A split bearing, comprising:aninner annular race having a longitudinal extent; an outer annular racehaving a longitudinal extent; a plurality of roller members; means forretaining the plurality of roller members between the inner race and theouter race; and a pair of annular clamps, wherein at least said outerrace includes at least two parts, each part defining two longitudinallyextending surfaces which mate with a corresponding longitudinal surfaceof the adjacent part, said surfaces defining a helix in theirlongitudinal extent, and said inner race includes a land on which saidplurality of roller members are engaged and a clamp recess having spacedapart longitudinally spaced apart edge on each side of said land forreceiving a respective one of said annular clamps, each clamp recessdefining longitudinally spaced apart edges, and wherein each clamprecess defines spaced apart annular lubricating grooves adjacent thelongitudinal edges of each clamp recess.
 9. A bearing, comprising:anannular inner race; an annular outer race; a plurality of rollermembers; and a cage for the roller members, said cage including twoannular parts that in assembly define a plurality of cavities each oneadapted to receive a roller member of said plurality of roller members,wherein each of said two annular parts including at least two piecesjoined together by a tongue and groove connection, and each cavity isdefined by said two annular parts with the longitudinally spaced edgesurfaces of each cavity being defined by a different one of said twoannular parts.
 10. The bearing as defined in claim 9, whereinsaidlongitudinally spaced edge surfaces are tapered radially outwardlytoward the center of the bearing.